Rotary kiln drive mechanism



June 21, 1966 J. A. MARLAND 3,257,104

ROTARY KILN DRIVE MECHANISM Filed July 20, 1964 5 Sheets-Sheet 1 FIEl lul

June 21, 1966 J. A. MARLAND ROTARY KILN DRIVE MECHANISM Filed July 20, 1964 June-21, 1966 J. A. MARLAND 3,257,104

ROTARY KILN DRIVE MECHANISM Filed July 20, 1.964

5 Sheets-Sheet .3

United States Patent 3,257,104 ROTARY KILN DRIVE MECHANISM Joseph A. Marland, 210 Blackstone, La Grange, Ill. Filed July 20, 1964, Ser- No. 383,661 7 Claims. (Cl. 26333) The present invention relates to drive mechanisms generally, and in particular to drive mechanisms employing rotary backstops.

One particular application for rotary backstops is in the drive mechanism of cement and other types of rotary kilns. Patent No. 2,910,286, entitled Rotary Kiln Drive Mechanism to Jens C. Holm discloses a drive mechanism for a cement kiln which employs two separate one-way clutches, one one-way clutch for coupling an emergency motor to a main drive shaft for the rotary kiln and the other one-way clutch as a portion of a backstop for preventing rotation of the cement kiln in a reverse direction. The present invention is directed to an improved one-way clutch backstop particularly adapted for use with cement kiln drive mechanisms of the type set forth in the Holm patent. For purposes of this application, a backstop may be defined as a device for preventing rotation of a shaft relative to its mounting structure in one direction while permitting its rotation in the reverse direction.

In the manufacturing of cement, a rotary kiln is disposed at an angle to the horizontal and rotated at a relatively slow rate. Such rotary kilns vary in length and may be several hundred feet in length. A homogeneous mixture of two materials, one material rich in lime and the other material rich in silica, is fed into the high end of the kiln. The kiln is continuously rotated, causing the mixture to pass from the high end of the kiln through the different zones of the kiln, known as the dehydration zone, the calcinating zone, and the clinkering zone. Heat is applied to the kiln as its rotates to produce a fusion of the mixture fed into the kiln, the fused mass being known as a cement clinker.

Such cement kilns are generally rotated by an electric motor coupled to the gear ring which surrounds the kiln. The electric power for the motor is generally obtained from commerical power lines, and hence it is necessary to provide an emergency motor to maintain the kiln in rotaa failure of power will spoil the batch in the kiln and may further damage the kiln itself because of the fact that the kiln is heated at one side and permitted to cool at the other side placing the kiln under thermal stress.

The device of the Holm patent, referred to above, provides a one-way clutch for coupling an emergency motor to the kiln in the event the electric motor fails to operate, and the emergency motor will continue to rotate the kiln. A one-way backstop is also used in the Holm device to prevent rotation of the kiln in the reversed direction, however, the one-way backstop has a release mechanism which is manually actuated. If the release mechanism is actuated to permit reverse rotation of the kiln, it is possible that a power failure will result in an unbalanced condition of the kiln producing reversed rotation which will drive both the primary electrical motor and the emergency motor at speeds which are self destructive. It is one of the objects of the present invention to provide a drive mechanism including a one-way backstop which is releasable, and when released limits the reverse rotation rate of the drive units.

Patent application Serial No. 200,833, filed June 7, 1962, now US. Patent No. 3,189,145, entitled, Releasable One-Way Clutch Backstop," of the present inventor and Charles W. Hill is directed to a one-way clutch backstop in which one of the races of the one-way clutch is anchored to the housing of the unit through an electro magnetic brake. The electromagnetic brake permits partial release of the backstop or full release of the backstop, and is actuatable from remote locations. However, when the electromagnetic brake of this backstop is deactuated, the shaft is free to rotate in any direction and is not retarded. It is an object of the present invention to provide a one-way clutch type backstop with a releasable brake mechanism coupling one of the races of the oneway clutch to the housing of the unit and a second brake mechanism coupling the same race of the one-way clutch to the housing of the unit which provides insufficient braking to prevent rotation of the shaft of the backstop, but which provides adequate braking to limit the rotation rate of the shaft to a safe permissible rate.

In addition to these objects, it is an object of the present invention to provide a simple, reliable, one-way backstop which is relatively inexpensive to construct and which is suitable for use with drive mechanisms of cement kilns.

These and further objects and advantages of the present invention will become readily apparent upon a further consideration of this specification, particularly when viewed in the light of the drawings, in which:

FIGURE 1 is a view illustrating a cement kiln and its drive mechanism, the kiln being illustrated schematically and the backstop in elevation;

FIGURE 2 is a view taken on the line 2-2 of FIG- URE 3 partly in section, and of FIGURE 1;

FIGURE 3 is a sectional view partly in elevation taken on the line 3-3 of FIGURE 2;

FIGURE 4 is a sectional view taken on the line 44 of FIGURE 3.

In FIGURE 1, a cement kiln 10 is fragmentarily illustrated. The kiln 10 is mounted on a pair of bearing means 9 located at each end of the kiln for rotation at an angle to the horizontal, as is conventional. The cement kiln 10 has a cylindrical steel drum 11 and a ring gear 12 extending thereabou-t. A layer 13 of refractory bricks is disposed on the interior surf-ace of the drum 11. The ring gear 12 is coupled to the low speed shaft 14 of a gear reducer 16, and the gear reducer 16 has a high speed shaft 18 which is coupled to an electric mot-or 20. During normal operation, the electric motor drives the kiln in the forward direction from power received from commercial electric lines.

As illustrated in FIGURE 1, the high speed shaft 18 of the speed reducer 16 is double extended, and a oneway clutch 22 is coupled to the end of the shaft 18 opposite the motor 20. The one-way clutch 22 is also coupled to the low speed shaft 24 of a second speed reducer 26. The second speer reducer 26 has a high speed shaft 28 which is coupled to a backstop 30. The backstop 30 also has a double extended shaft 32 which is coupled at its end opposite the speed reducer 26 to an emergency motor 34, such as an internal combustion engine.

The one-way clutch 22 is connected to free wheel aslong as the motor 20 is operating at a speed in excess of the low speed shaft 24 of the speed reducer 26. When the low speed shaft 24 of the speed reducer 26 is driven at a higher rate than the electric motor 20 by the internal combustion engine 34, the one-way clutch 22 becomes engaged and drives the high speed shaft 18 of the main speed reducer 16, and hence the cement kiln 10.

The backstop 30 is illustrated in detail in FIGURES 2, 3, and 4. The shaft 32 extends through two walls 36 and 38 of a housing 40, the housing having openings 42 and 4-4 to accommodate the shaft 32. A roller bearing assembly 46 is mounted in the opening 42 of the wall 36 and has an inner race 48 which engages the exterior surface of the shaft 32, and outer race 50 which engages the surface of the opening 42, and a plurality of conical rollers 52 between the races 48 and 50. A cover 54 with 3 a central opening to accommodate the shaft 32 is mounted on the wall 36 of the housing 40 to seal this surface of the housing. In like manner, a second roller bearing assembly 56 is mounted in the opening 42 of the wall 38 and journals the shaft 32. A second cover 58 with a central opening for accommodating the shaft 32 closes the wall 38.

The shaft 32 has a portion 60 disposed centrally between the walls 36 and 38 which has an exterior surface forming the inner cam of a one-way clutch. The portion 60 of the shaft 32 has a cylindrical surface 62 which is provided with a plurality of indentations 64. Each of the indentations 64 has a fiat surface 66 disposed parallel to the axis of the shaft 32 and at approximately the same angle to the tangent to the surface 62 as the flat surface 66 of the other indentations 64. A groove 68 is disposed parallel to the axis of the shaft 32 at the end of each flat surface 66 remote from the surface 62 of the shaft.

A cylindrical roller 70 is disposed in each indentation of the portion 60 of the shaft 32, and each roller is maintained in position between two rings 74 and 76 which extend about the portion 60 of the shaft. A spacer 78 is disposed between adjacent cylindrical rollers 70 and has concave sides 80 confronting adjacent rollers. The spacers 78 are mounted on the rings 74 and 76 to form a cage for the rollers 78.

A cylindrical cuter race 82 is disposed about the portion 60 of the shaft 32 and has a cylindrical surface confronting the assembly of rollers 70. The outer race 82 is mounted on a pair of spaced ball bearing assemblies 84 and 86. A rim 88 extends outwardly from the cylindrical outer race 82 in a plane normal to the shaft 32, and a gear rim 90 is mounted on the rim 88 by a flange 92 extending inwardly therefrom and a plurality of equally spaced bolts 94 and nuts 96.

, A worm gear 98 which is integral with a second shaft 100 disposed normal to the shaft 32 is meshed with the gear rim 90. The second shaft 100 is journaled within two roller bearing assemblies 102 and 104 which are disfree wheeling direction of the one-way clutch formed by the portion 60 of the shaft 32, the roller bearing assembly, and the outer race 82. The centrifugal brake 116 is designed to provide a drag on rotation of the shaft 100 to limit the rotation rate of the shaft 32 to safe and permissible limits in thereverse direction of rotation.

The shaft 100 extends through the wall and is keyed by a shaft key 118 to a hub 120 of rectangular cross section. The hub 120 is disposed within rectangular openings 122 of two identical friction plates 124 and 126 which are disposed in parallel spaced relation. A brake disc 128 is disposed between the friction discs 124 and 126 and anchored on the housing 130 of the releasable electromagnetic brake by a plurality of parallel spaced ribs 132 which protrude inward parallel to the shaft 100 from the housing 130. A brake pressure plate 134 is disposed on the side of the friction disc 126 remote from the housing 40, and a spring bias pressure means continuously urges the pressure plate 134 into engagement with the friction plate 126 to wedge the two friction plates 124 and 126 between the pressure plate 134, the brake disc 128, and the surface 136 of the housing confronting the friction plate 124..

Mechanisms have been known prior to the present invention for maintaining the brake pressure plate 134 under tension in a direction to compress the friction plates 4 4 124 and 126 on the brakering 128, and such prior mechanisms also have been provided with magnetic releases and manual releases. Patent No. 3,045,782 of Hense entitled, D'etent for Releasa'bly Holding an Electromagnetic Brake Disengaged, is an example of a suitable mechanism for the electromagnetic brake 114. In the mechanism of the Hense patent, which is shown in FIGURE 3, an arm 138 is pivoted on a pin 140' and placed under spring tension by a spring 142 to engage the pressure plate 134 at a point designated 144. The arm 138 may be released by actuating the electromagnet 146, or by effecting the same action by pulling the plunger 148 outwardly.

FIGURES 3 and 4 illustrate the construction of the centrifugal backstop. The centrifugal backstop has a cylindrical drum 150 which is mounted on the wall 112 of the housing 48 by means of a circular flange152 and a plurality of bolts 154 extending at equal intervals about the perimeter of the drum. The drum 150 also has a cylindrical recess 156 coaxially disposed about the protruding end of the shaft 180. I

A brake shoe assembly 158 is mounted on the end of the shaft 180 confronting the cylindrical surface 156 by means of a hub 161) having an axial opening which engages the end of the shaft 188. The hub has a plate 162 which extends radially outwardly therefrom in a plane normal to the axis of the shaft 100, and the plate has a plurality of indentations 164 equally spaced about its perimeter. A brake shoe 166 is disposed in each of the indentations 164 and has a layer 168 of brake lining disposed thereon confronting the cylindrical surface 1-56 of the drum 158. The brake shoe is mounted on the plate 162 by an interconnecting flexible rubber bushing 170. The bushing 170 is capable of stretching in response to rotation of the shaft 100 to permit the brake shoe 166 to abut and engage the cylindrical surface 156 of the drum 158.

A cylindrical sleeve 172 extends through each bushing 170, and a bolt 174 disposed within the sleeve anchors a pair of links 176 and 178 at one end thereof. The opposite end of the links 176 and 178 at one end thereof. The opposite end of the links 176 and 178 are anchored pivotally on a second pin 180- mounted on the protruding portion of the plate 162. The pins 180 are mounted in rubber grommets 182 so that tightening of bolts 184 at the ends of the pins 180 resists angular deflection of the links 176 and 178. In this manner, the rotation rate of the brake shoe assembly 158 which will result in engagement of the brake shoes 166 and the cylindrical surface 156 of the drum 150 can be selected and determined.

It is to be understood that other types of centrifugal clutches may also be employed for the centrifugal clutch 116' in accordance with the present invention, such as the clutch disclosed in Patent No. 2,588,482 of Chapman entitled, Friction Clutch, BrakeQand Coupling.

The drum 150 is constructed of metal material having a large thermal capacity so that a substantial quantity of heat may be stored in the drum 150 without a substantial temperature rise which would affect the life of the lining 168 on the brake shoes 166. In practice, the drum is designed to limit the temperature rise to approximately degrees in the event the brake shoe 166 engages the cylindrical surface 156 for a period of ten minutes under full load conditions. This is achieved by providing an aluminum drum 150 with a diameter of 11 /2 inches and a thickness of 2 /2 inches, the diameter of the cylindrical surface 156 being approximately 3 inches.

During normal operation, the main drive electric motor 20 operates and rotates the kiln 10, and the one-way clutch 22 prevents rotation of the high speed shaft 18 of the speed reducer 16 from transmitting power to the backstop 38 or internal combustion engine 34. As a result, unless there is occasion to operate the internal combustion engine 34, the free wheeling clutch formed by the portion 60 of the shaft 32, rollers 70, and outer race 82 will not have occasion to operate. In order to make cercombustion engine 34 from overspeed.

tain that an adequate supply of lubricant is immediately received upon rotation of the shaft 32, two cylindrical discs 186 and 187 are mounted normally on the shaft 32 at opposite ends of the outer race 82, and these discs 1 86 and 187 and the gear rim 90 extend downwardly into a pool of liquid lubricant 188, such as oil, disposed in the housing 40'. As a result, lubricant will be splashed throughout the interior of the housing 40 due to rotation of the shaft 32, thereby lubricating the one-way clutch mounted on the shaft 32, the gear rim 90 and the Worm gear 98.

If the electric power to the main electric motor 20 should fail, internal combustion engine 34 may be started, and will drive the shaft 32, and hence the kiln in the same direction as it was driven by the main drive motor 20. The one-way clutch of the backstop 30 free wheels under these conditions. When electric power is restored to the electric motor 20, it will drive the kiln 10 at a higher rate of speed than the internal combustion engine 34, and hence, the electric motor 20 will take over control of the kiln by the action of the one-way clutch 22. Should a power failure occur to the electric motor 20 and the internal combustion engine 34 be inactivated, the load of a batch within the kiln will tend to reverse rotation of the kiln 10. However, in order to reverse the rotation of the kiln 10, the shaft 32 of the backstop 30 must be reversed in rotation, and the one-way clutch formed by the portion 60 of the shaft 32, the rollers 70, and the outer race 82 will transmit torque to the shaft 100. The releasable electromagnetic brake 114 is normally maintained in an inactuated condition, that is, a condition in which the shaft 100 is mechanically coupled to the housing 40 so that the shaft 100 may not rotate relative to the housing 40. As a result, the backstop 30 prevents rotation of the kiln 10 in the reverse direction.

When it is desirable to reverse the direction of rotation of the kiln 10, either for relining of the layer 13 of bricks on the interior of the kiln or other purposes, the electromagnetic brake 114 is inactuated by applying electric power to the solenoid 146. In the event of a power failure, the brake 114 may be released by mechanically actuating of the plunger 148. As a result of releasing the electromagnetic brake 114, the shaft 100 is free to rotate and will be driven by the gear rim 90 through the one-way clutch as a result of torque placed upon the shaft 32. Rotation of the shaft 100 causes the brake shoe assembly 158 of the centrifugal brake 116 to rotate, thereby causing the brake shoes 166 to tend to engage the cylindrical surface 156 of the drum 150. As the rotation rate of the brake shoe assembly 158 increases, the brake shoes 166- create increasing friction with the drum 150' to retard and limit the rotation rate of the shaft 100. Limitation of the rotation rate of the shaft 100 limits the rotation rate of the shaft 32, and hence protects the internal In a particular construction of the present invention, the internal combustion engine is designed for operation at 1800 revolutions per minute and the centrifugal brake 116 is effective to limit rotation of the shaft 32 to rates less than 1800 revolutions per minute.

It is to be noted that a centrifugal brake 116 may be a relatively light duty unit, and so may the electromagnetic releasable brake 114, since these units operate to limit rotation and brake shaft 100, thereby taking advantage of the torque reduction afforded by the worm gear 98 and gear rim 90. In addition, worm gear 98 and gear rim 90 achieve a speed multiplication which provides the centrifugal force required to force the brake shoes 166 into abutment with the cylindrical surface 156 and provide a slow enough rotation rate of the kiln for control.

Those skilled in the art will readily devise applications for the present invention beyond those here set forth. Further, those skilled in the art will readily modify the construction here disclosed within the concept of the present invention. It is therefore intended that the scope of the present invention be not limited by the foregoing disclosure, but rather only by the appended claims.

The invention claimed is:

1. A rotary kiln comprising, in combination, a drum, a brick liner disposed on the interior surface of the drum, means for rotatably mounting the drum at an incline to the horizontal, a drive mechanism mechanically coupled to the drum including a motor, and a backstop mechanism coupled to the kiln to prevent rotation of the kiln in a reverse direction including a shaft coupled to the motor, a one-way clutch having a first race mechanically coupled to the shaft for rotation therewith and a second race coaxially disposed relative to the first race, a plurality of drive elements disposed between the first and second races for permitting rotation of the first and second races relative to each other in the forward direction of rotation of the kiln, said drive elements wedging between the races for torques exerted between the races in the reverse direction, a releasable braking mechanism operatively associated with the second race, and a centrifugal brake mechanically coupled to the second race for limiting the rate of rotation of the second race when the releasable braking means releases the second race for reverse rotation.

2. A one-way backstop adapted to release a load for rotation in the reverse direction at a limited rotation rate comprising a shaft adapted to be mechanically coupled to the load, a one-way clutch having a first race mechanically coupled to the shaft for rotation therewith and a second race coaxially disposed relative to the first race,

a plurality of drive elements disposed between the first I and second races for permitting rotation of the first and second races relative to each other in the forward direction of rotation of the load, said drive elements wedging between the races for torques exerted between the races in the reverse direction, a releasable braking means operatively associated with the second race, and a centrifugal brake mechanically coupled to the second race for limiting the rate of reverse rotation of the second race when the releasable braking means releases the second race for reverse rotation.

3. A one-way backstop comprising, in combination: a first shaft adapted to be coupled to a load; a one-way clutch having a first member mechanically coupled to the first shaft and defining a cylindrical inner race coaxially disposed about the first shaft, said one-way clutch having a second member defining a cylindrical outer race coaxially disposed about the inner race, and said clutch having a plurality of drive elements disposed between the inner and outer races, said drive elements Wedging between the races for torques exerted in one direction between the races and slipping freely between the races for torques exerted between the races in the opposite direction, said second member of the one-way clutch carrying a gear coaxial with the first shaft; a second shaft rotatably mounted normal to the first shaft and having a worm gear confronting the second member of the one-Way clutch and meshed therewith; a releasable brake mechanically coupled to the second shaft; and a centrifugal brake mechanically coupled to the second shaft.

4. A one-way backstop comprising the elements of claim 3 in combination with means defining a pool of liquid lubricant below and adjacent to the first shaft, the gear rim being partially emersed in the pool of liquid lubricant.

5. A one-way backstop comprising the combination of claim 3 wherein the releasable brake comprises an elec tromagnetic brake provided with a manually operable release mechanism.

6. A one-way backstop comprising, in combination: a housing. having a cavity therein defined by two pair of parallel walls, the first pair being disposed normal to the second pair, each ofthe walls of the first pair having an opening therein disposed on a first axis normal to the walls of the first pair, and each of the walls of the second pair having an aperture disposed therein on a second shaft Within the apertures of the second pair of Walls;

said first shaft having a plurality of indentations spaced about the perimeter thereof and confronting the second shaft, each of said indentations having an incline plane portion disposed at the same acute angle to the tangent to the shaft at the intersection of the incline plane portion; a roller disposed within each indentation, a cylindrical sleeve disposed about the first shaft confronting the rollers, said rollers Wedging between the sleeve and first shaft for rotational torques in one direction between the sleeve and first shaft and free wheeling for rotational torques in the opposite direction; a first gear coaxially disposed about and mounted on the sleeve; a Worm gear disposed coaxially about the second shaft and meshed.

with the first gear; an electromagnetic brake mechanism mounted on the housing exterior thereof and mechanically coupled to the second shaft; and a centrifugal clutch mechanism mounted on the housing exterior thereof and mechanically coupled to the second shaft, said centrifugal clutch limiting the maximum rotation rate of the second shaft to limit the rotation rate of a load coupled to the first shaft during periods'when the electromagnetic brake is disengaged.

7. A rotary kiln comprising, in combination, a drum, a brick liner disposed on the interior surface of the drum, means for rotatablymounting the drum at an incline to the horizontal, a drive mechanism mechanically coupled to the drum including a motor, a releasable backstop mechanism coupled to the kiln to prevent rotation of the kiln in a reverse direction including a shaft coupled to the motor, a oneay clutch having a first race mechanically coupled to the shaft for rotation therewith and a second race coaxia'lly disposed relative to the first race, a plurality of drive elements disposed between the first and second races for permitting rotation of the first and second races relative to each other in the forward direction of rotation of the kiln, said drive elements Wedging between the races for torques exerted between the races in the reverse direction, and a centrifugal brake mechanically coupled to the second race for limiting the rate of rotation of the second race when the backstop mechanism is released for reverse rotation of the kiln.

References Cited by the Examiner UNITED STATES PATENTS 2,910,286 10/1959 Holm 26323 JOHNJ. CAMBY, Acting Primary Examiner. 

7. A ROTARY KILN COMPRISING, IN COMBINATION, A DRUM, A BRICK LINER DISPOSED ON THE INTERIOR SURFACE OF THE DRUM, MEANS FOR ROTATABLY MOUNTING THE DRUM AT THE INCLINE TO THE HORIZONTAL, A DRIVE MECHANISM MECHANICALLY COUPLED TO THE DRUM INCLUDING A MOTOR, A RELEASABLE BACKSTOP MECHANISM COUPLED TO THE KILN TO PREVENT ROTATION OF THE KILN IN A REVERSE DIRECTION INCLUDING A SHAFT COUPLED TO THE MOTOR, A ONE-WAY CLUTCH HAVING A FIRST RACE MECHANICALLY COUPLED TO THE SHAFT FOR ROTATION THEREWITH AND A SECOND RACE COAXIALLY DISPOSED RELATIVE TO THE FIRST RACE, A PLURAL- 